if (isset($_POST['login_user'])) {
$username = mysqli_real_escape_string($db, $_POST['username']);
$password = mysqli_real_escape_string($db, $_POST['password']);

if (empty($username)) {
    array_push($errors, "Se requereix nombre de usuari");
}
if (empty($password)) {
    array_push($errors, "Se requereix contrasenya");
}

// Quan et loguejes sense errors
if (count($errors) == 0) {
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
    $results = mysqli_query($db, $query);
    if (mysqli_num_rows($results) == 1) {
        $_SESSION['username'] = $username;
        $_SESSION['success'] = "Ara estàs conectat";
        header('location: ../index.php');
    }
    else {
        array_push($errors, "Combinació usuari/contrasenya malament");
    }
}

<div class="row">
    <div class="main">
        <a name="jocs">
            <table class="table_jocs">
                <tr align="center">
                    <td><h2>Typer</h2></td>
                    <td><h2>Brainer</h2></td>
                    <td><h2>PPT</h2></td>
                    <td><h2>Draw me!</h2></td>
                </tr>
                <tr>
                    <td><a href="/typer" target="_blank"><img src="/imagens/mecanografia.png" class="iconos_jocs"></a></td>
                    <td><a href="/brainer" target="_blank"><img src="/imagens/brainer.png" class="iconos_jocs"></a></td>
                    <td><a href="/pedra_paper_tisores" target="_blank"><img src="/imagens/ppt.png" class="iconos_jocs"></a></td>
                    <td><a href="/draw" target="_blank"><img src="/imagens/dibuix.png" class="iconos_jocs"></a></td>
                </tr>
                <tr align="center">
                    <td><h2>Velocity</h3></td>
                    <td><h2>Were's Wally?</h2></td>
                    <td><h2>Bowser Game</h2></td>
                    <td><h2>Moveless</h2></td>
                </tr>
                <tr>
                    <?php if (($_SESSION['premium']) == 'si') { ?>
                        <td><a href="/velocity" target="_blank"><img src="/imagens/velocity.png" class="iconos_jocs"></a></td>
                        <td><a href="/wally" target="_blank"><img src="/imagens/wally.png" class="iconos_jocs"></a></td>
                        <td><a href="/bowser" target="_blank"><img src="/imagens/bowser.png" class="iconos_jocs"></a></td>
                        <td><a href="/moveless" target="_blank"><img src="/imagens/ma.svg" class="iconos_jocs"></a></td>
                    <?php } ?>
                </tr>
            </table>
        </a>
    </div>
</div>

if (isset($_POST['login_user'])) {
$username = mysqli_real_escape_string($db, $_POST['username']);
$password = mysqli_real_escape_string($db, $_POST['password']);

if (empty($username)) {
    array_push($errors, "Se requereix nombre de usuari");
}
if (empty($password)) {
    array_push($errors, "Se requereix contrasenya");
}

// Quan et loguejes sense errors
if (count($errors) == 0) {
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
    $results = mysqli_query($db, $query);
    if (mysqli_num_rows($results) == 1) {
        $fila = mysqli_fetch_array($resuls)//Debes obtener el resultado
        $_SESSION['username'] = $username;
        $_SESSION['premium'] =  $fila[0]['premium'];//Obtienes el valor de
                                                    //la columna premium
        $_SESSION['success'] = "Ara estàs conectat";
        header('location: ../index.php');
    }
    else {
        array_push($errors, "Combinació usuari/contrasenya malament");
    }
}

if (count($errors) == 0)
{
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
    $results = mysqli_query($db, $query);
    $fila = mysqli_fetch_array($resuls) //Variable $fila
    if (mysqli_num_rows($results) == 1)
    {
        $_SESSION['username'] = $username;
        $_SESSION['success'] = "Ara estàs conectat";
        header('location: ../index.php');
    }
    else if (mysqli_num_rows($results) == 1 && $fila['premium'] == "si")
    {
        $_SESSION['premium'] = "si";//Variable para saber si el usuario es premium
        $_SESSION['username'] = $username;
        $_SESSION['success'] = "Ara estàs connectat usuari premium";
        header('location: ../index.php');
    }
    else
    {
        array_push($errors, "Combinació usuari/contrasenya malament");
    }
}